The present invention relates generally to tools and methods for brushing, and will be specifically disclosed as a machining tool and method for brushing the inner surface of a bore.
In a variety of different applications and industries, it is desirable to brush the surfaces in and around machined holes. For instance, machining parts such as metal stock of steel or some other alloy, are often designed with a hole or bore. Typically, the rough dimensions of the bore are initially cast and/or machined, and then one or more subsequent machining steps are required to achieve the final bore dimensions. In some applications, (e.g. boring engine cylinders), a finishing honing operation is also performed on the inner surface of the bore. After a bore is machined and honed, it is known to brush the inner surface to remove residual metal shavings or fines that may remain after the machining or honing operations. If this residual material is not removed, application of the part may cause damage to the part, or corresponding apparatus. For instance, failure to remove residual metal shavings from the bore of an engine cylinder may contaminate the oil supply of the engine in use. As a result, the lubricating oil may be reduced to an abrasive slurry that can be detrimental to engine/pump life.
As with other machining steps and processes, it is desirable to minimize cycle time while maximizing tool life. In brushing operations, cycle time can be minimized by applying increased force between the brush and the material being brushed (e.g., between the brush and the interior bore surface). However, if too much force is applied by the brush to the material, the brush may undesirably crack or even fail. Furthermore, conventional brushes typically wear during use, thereby requiring mechanical and/or manual adjustment of the brushes so that the desired force can be maintained. Such adjustments can be time consuming, since known conventional brush adjustment cannot be accomplished while the tool is simultaneously performing a brushing operation. Known brush adjusting techniques are also inaccurate whereby the desired force being applied to the material is not achieved. Moreover, adjustment during non-use will not compensate for wear or the varying force being applied to the material that can occur during a tool cycle.
In almost all machine tool operations, including brushing, the friction between the tool and workpiece generates a tremendous amount of heat energy that can result in temperatures reaching 2000xc2x0 F. (1100xc2x0 C.) and above. If left uncontrolled, such excessive temperatures may severely damage (e.g., cracking or fracturing) the tool, thereby reducing its tool life, making machine tool operations more dangerous and expensive, and/or reducing the quality and precision of the workmanship. In addition, heat generated friction can discolor the workpieces, and can damage or remove temper or heat treatments. It is commonly known in the industry that coolant can be introduced to the machining area, such as by spraying, to reduce friction between the tool and workpiece by maintaining a thin film of coolant fluid between the tool and the workpiece, and to help remove heat energy generated in machine tool operations.
Although coolant fluid can be supplied to the brushing area, it is often difficult to ensure that such fluid actually makes its way to the interstices between the tool and all of the workpiece surfaces being machined. Additionally, fluid tends to evaporate quickly due to the high temperatures involved in brushing operations. Thus, larger volumes of coolant fluid must generally be continuously supplied to the brushing area for effective brushing tool operation. The desire to maintain coolant fluid between the brushing tool and inner surface of the bore becomes even more problematic in operations where coolant fluid cannot be introduced in close proximity to the brushing areas while the brushing tool is being used to brush the bore surface.
During operation, the work engaging surface (e.g., brushes) of the tool can also become loaded with particles or recently cut chips from the surface of the workpiece, which in turn, reduces the accuracy and effectiveness of the tool through deteriorating brushing ability, and/or clogging of conventional coolant fluid supply openings. It is obviously preferred to reduce the undesired loading of particles, and that any loaded particles be promptly removed from the brushing tool. Conventional nozzle arrangements are often provided with an independent external cleaning jet for injecting coolant fluid. Typically, the cleaning jet is designed to direct a high velocity stream of fluid toward the work engaging surface and the work surfaces of the workpiece to wash away particles, to remove residual particles from the work surface, and to cool the brushing tool and the workpiece. However, as mentioned previously, it is often difficult to ensure that the fluid sprayed in this way actually reaches the most critical areas of the tool/workpiece interface.
Other attempts to deliver coolant fluid to the brushing area have included air or other pneumatic carriers. As with externally applied liquid coolants, pneumatic carriers typically result in turbulence that can hinder the brushing operations, and may not permit fluid from infiltrating into the actual brushing area. Previous attempts to address these cooling and cleaning requirements often tend to reduce the accuracy and utility of the tool.
As can be seen, conventional brushing tools have a number of shortcomings that can greatly reduce the tool""s life, its effectiveness, and the ability to use it with an automatic tool changing system. The current structures and assemblies of brushing tools do not provide a generally constant force between the brush and the workpiece being brushed which can result in shaving and chips not being removed from the machined piece.
Accordingly, it is an object of the present invention to address and obviate problems and shortcomings of conventional brushing tools.
It is a further object of the present invention to provide an improved brushing tool that has an increased tool life.
It is a further object of the present invention to provide an improved performance brushing tool that can be selectively adjusted during machining operations.
It is yet another object of the present invention to provide an improved brushing tool that can be easily removed from a tool mandrel.
Still another object of the present invention is to provide our improved brushing tool that can be used with a quick change or automatic changeable tool system having a source of pressurized fluid.
A further object of the present invention is to provide an improved brushing tool which can regulate itself to adjust for wear and tear on the brushes.
Another object of the present invention is to provide a tool and method for brushing surfaces, such as the inner surfaces of a bore in a workpiece.
To achieve the foregoing and other objects in accordance with the present invention, tools for brushing an inner surface of a hole are provided including a rotatable shaft, an inlet in fluid communication with a source of pressurized fluid, at least one outlet positioned so as to wet an inner surface of a hole, and a flow path extending between the inlet and the outlet. The tool further includes at least one brush being radially moveable relative to the shaft to an extended position and a retracted position, wherein the brush is adapted to move to the extended position when the shaft is rotating and a brush retractor connected to the brush.
To achieve further objects in accordance with the present invention, tools for brushing an inner surface of a hole are provided with a mandrel capable of being rotated about an axis. The tool further includes a fluid channel in the mandrel having an inlet for receiving pressurized fluid and at least one outlet for wetting an inner surface of a hole and a brush assembly attached to the mandrel comprising at least one brush. The brush assembly being radially moveable relative to the mandrel to an extended position and a retracted position. The brush assembly is also adapted to move to the extended position at least in part due to an outward radial force generated by the rotation of the mandrel when the mandrel is rotating.
To achieve still further objects in accordance with the present invention, tools are provided for brushing an inner surface of a hole. The tool includes a mandrel capable of being rotated about an axis and a fluid channel in the mandrel having an inlet for receiving pressurized fluid and an outlet for wetting an inner surface of a hole. A brush assembly is also included with at least one brush attached to a brush mount and one or more supports attached at one end to the brush mount and slidably attached to the mandrel at the other end. The brush assembly is radially moveable relative to the mandrel to an extended position and a retracted position. In addition, the brush assembly is adapted to move to the extended position at least in part due to an outward radial force generated by the rotation of the mandrel when the mandrel is rotating. A brush retractor is capable of inducing a radially inward load on the brush assembly thereby biasing the brush assembly toward the retracted position. The mandrel may be rotated such that the inward load is less than the outward force thereby orienting the brush assembly in the extended position.